Re: [RFC PATCH v2] grep: allow for run time disabling of JIT in PCRE

Hi,

On Mon, 29 Jul 2019, Carlo Marcelo Arenas Belón wrote:

My immediate reaction to this error message was: That's not helpful. What is `-48` supposed to mean? Why do we even think it sensible to throw such an error message at the end user? Can't we do a much better job translating that into something that makes actual sense without knowing implementation details?

But then, I realized that -48 must be a well-known constant in PCRE2, and my reaction transformed into something much more hopeful: why don't we detect the situation where the JIT'ed code was not actually executable [*1*], and fall back to the non-JIT'ed code path ourselves, without troubling the end user (maybe warning, but maybe better not lest we annoy the user with something pointless)?

Even after finding out that -48 disappointingly means PCRE2_ERROR_NOMEMORY (as opposed to something like PCRE2_ERROR_CANNOT_EXECUTE_JIT_CODE), I like the idea of not bothering end users and doing the sensible fallback under the hood.

Ciao, Dscho

Footnote *1*: Why anybody would think it sensible to build a PCRE2 with JIT on an OS that does not allow executing code that was written by the same process is beyond me. Or is there a mode in OpenBSD that *does* allow JIT'ed code to be executed?